Method of increasing the supporting strength of conduits



May 29, 1928. 1,671,679

A. MARSTON V METHOD OF INCREASING THE SUPPORTING STRENGTH OF' CONDUITSFiled Sept. 12, 1924 l Patented May 29, 1928s. l

UNITED( STATES o i 1,671,679 PATENT OFFICE.-

ANBON MARBTON, 0F AMES, IOWA, ASSIGNOB T0 IOWA STATECOLLEGE OFGBICUL-TUBE AND MECHANIC ARTS, 0F AMES, IGWAyAL CORPORATION 0F IOWA.. i

mE'rHon on' INCBEASINGKTHE SUPPORTING STRENGTH or `ooimurrfs.

Application `tiled September 12, 1924. 4 Serial No. 787,371.`

VVlnenr large conduits `of concreteorfother material are` laid intrenches,` und` the trenches are subsequently filled with earth or othermaterial,` and also when 4suoli `are laid on an solid surfaceprOJeGtmgu'pwardly into" lied areas, it` frequently 0ccurs that theconduits 'will be cracked or crushed afterltheearthsettles.; This isowing to insufficient supportingstrength of the conduit, which at times,is often `partly, due

to the tact that it frequently happenslthat a duit is y iirmly and`uniformly supported throughout its length, softhatf crushing strains apliedto the u per surfaces will be resisted y the entire ody oftheconduit,

`and will not be unevenly distributedlupon `certain points or partsthereof", L g

A further object is to provide an imf proved' method of reinforcing thetop "portion es well as the sidesl and bottolnjportions l of conduiteS05 asto give greater inherent supporting 4'strength to resist crushingstrains` d 'fo l `My invention consists 1n the method of metal andconcrete atthe `bottom and sides of a conduit, whereby the conduit- Hisuniformly and evenly supported "at its bottom, andalso in the improved`method of applyingreili- `forcing metal and concrete around `theconduit,

whereby objects 'contemlatedy are attalned, as hereinafter more ully setforth, pointed out in my claims, Iand' illustrated inthe accompanyingdrawings, 1n` which:

, force by my improved method, with c portion ofthe trench adjacentthereto `prepared in accordance with my improved Imeth'od to receive a"conduit and reinforcing metal and concrete. A y i Figure 2 shows atransverse sectional View kthrough a `trench and a conduit providedlwith, reinforcements applied in accordance with myimproved method. c ov y o Figure 3 shows a transverse sectional view of a trench havingportions of its bottom and sides cut` away as required in carrying outmy imprOVedmethod; and f Figure 4 shows atransverse sectional viewthrouh a trench and culvert showing a,de` vice o y t "and, meta-ly atthe upper portions of the conor` retaining the reinforcing;` concreteduits, andfllustrating one means' by which my improved method may becarried out. y Betel-rino. to the `accompanying drawings,

I'have `illus rated an ordinary trench formed in the earth to `receive"a conduit. The boty tomof the trench is indicated generally by thenumeral 10 and the sides are indicated generally by the numeral 1l. Mymethod `is,

also used for conduits notlad in trenches,l but '-the conduit which isof the ordinary kind 110W` lncolnnion `use is indicated by the numeral12. r y l Before laying each section of conduit, the

` operator employs a rounded spade or `other implement land `scoops outfrom the hottom ofthe trench,` or from any other solid` sm'- Vface on`which the conduit is' to laid, two or y more rounded curved depressions13.' `When the conduit islaldfm a trench so narrowas to require it, healso, directly above each ond of thedepression 13", scoops out a roundedsemi-cireularjrec'ess 14 from the earth at the "sides of the trench. Hethen places metal y i y' reinforcing wires, rods or barsl in thedekpreparing; the trench to receive relnforclngfprgggong `,133, and"yalso; other reinforcing vWires, rods or harsl and 17 respectively at`the sides and top of the conduit. The reinforcing Wires, rods or bars115,116 and 17in-ay y be combined. The double lines of reinforc` rings"leerecastbefore the culvert put into position,I but when the reinforcingapplied after the conduit is laid, the outside reinforcing bars 15, 16,17 and`18 may be omitted. o y

The operator then places a quantity of concrete material in theldepressions, 13, and then `heolaces the conduit in position resting uponsaid concrete material, and also upon the hottolnof the trench, or othersolid sul face on rwhich the conduit is laid. between the depressions13. After this vhasbeen done, heplacesconcretematerial around the sidesand top of the conduit and around the reinforcim'er hars `16 and/17toform projecting rings 18 of reinforcedconcrete around the `body of theconduit, assliown inFigure 1. o

When lacing this concrete lmaterial to form reinibrcin rings 18, it issometimes desirable to empiiiy a series of concrete retainingy forms 19in the trench-on `opposite sides of the particular ring 18 which is thenbeing formed of concrete material, and this is necessary when theconduit is not laid in a trench. These retaining forms 19 may be shapedas illustrated in the drawings, with their side edges of a width toloosely tit the interioi of the trench, and their lower ends shaped toproject downwardly between the conduitand the adjacent sides of thetrench, to thereby prevent the concrete material from moving indirections longitudinally of the conduit. The retainin forms must havean outer member when tie conduit is not laid in a trench. When theconcrete material has set, these retaining forms may be removed andrepeatedly used. The various reinforcing wires, rods or bars 15, 16 and17 are arranged with theirends inoverlapping position within theconcrete material, thus forming the reinforced continuous rings 18completely encircling the conduit.

In practice with my improved method of increasin@ the su ortino stren liof conduits, I have found that thesupporting` strength of the conduitsmay be increased to a very considerable extent at a comparatively slightcost, because the work of preparing the depressions and' recesses atthebottoml and sides of the trench can be very quickly and easily done byordinary workmen, and these recessesand depressions perform the doublefunction of providing a means Whereby the reinforcing concrete materialmay be easily positioned under and at the sidesofAV the conduit, andthey also form a sort of mold or receptaclein which this concretematerial andreinforcen'ient can be retained while setting and hardening.However, 1n

some cases I find it desirable to construct my` reinforcing rings 18around the conduit before laying it in position.

.The results, as to increasing the support ing strength of the conduitswhen my improved method is practiced, are much greater than thoughthe'corresponding amount of reinforcing concrete and metal were appliedLto the conduitsotherwise, because no matter how much reinforcement isapplied to the conduits, their resistance to crushing strains depends toa material extent upon whether or not their bottom and sidey portions`rest firmly and uniformly upon a solid founda- 18 around the conduitbefore placin tion, which cannot be obtained by simply laying thereinforced conduits on the bottom of an ordinary trench. In cases whereI find it desirable to construct my reinforcing rings it in position, Imake the depressions 13 s ightly larger than the exterior of the rings18 and insert soft concrete between the rings and the earth.

Vare `sup orted inl such a `wa Furthermore, the strength added to aconduit by lnetal reinforcing depends to a large degree upon thedistance between the outer and inner reinforcing bars, which inmy^improved method may be veryf large in the reinforcing rings 18 as comaired with the small distance availablein t ecomparatively thin shell orwall of the conduit.

Furthermore, accordin to my improved method, the conduits'are rmly heldagainst longitudinal movement in the trench. y

When the 'bottom and sides of a conduit that the sides cannot distortedoutwal pressure I0 `in yresisting crushin ,strainsl from above ismaterially. increase and according'y to my method, the concretereinforcements that engage the sides of the` culvert are held togetherby the reinforcements imbedded in concrete thatextend across the top ofthe culvert. Hence, pressures applied on topy of the culvert will be.resisted in their tendency to distort the sides of the culvertoutwardly,by such reinforcements at the top,

I. claim as my invention: f v

1. The method of increasing the supporting strength of conduits Aintrenchesor projected into filled areas, which consists in p `firstforming in the earth a trenchhaving a. bottom surface and side walls,said bottom surface being formed to. receive and support precastconduits, then cutting into the earth in said bottom and sides of theearth trench wall forv the transverse depressions at the .side of thetrench, and rfinally placing plas- U0 tic concrete material in thedepressions and recesses at the bottom and sides of the conduit, saidplastic concrete filling said transverse depressions and engaging boththe earth at the bottom and sides lthereof andll the concrete at the topand innerface thereof. .f l

2. The method 4of increasing the supporting strength of conduits intrenchesor pro-` jected. into filled areas, which consists in l firstforming in the earth a trench having abottom surface and side walls,saidbottom ,surface being formed to receive and support recast conduits,thencutting into the earth 1n said bottom and sides ofthe earth trench la series of spaced transversely extended depressions, then placin aconduit in position i with portions thereo resting u on the bottoni ofthe trench which ha previouslyV been shaped to receive it, and otherportions l.

1,s71,e79 y 3 thereof projecting across said transverse versedepressions and engaging both the 10 depressions, and whereby theconduit itself earth at the bottom and sides thereof and forms a -topfor the transverse depressions the concrete at the top and inner facetherein the bottom of the trench and an inner of, and then placingconcrete material over 5 Wall for the transverse depressions at the thetop portion of the conduit in line with kside of the trench, and iinallplacing plasand Vforming a continuation of the concrete 15 i ticconcrete material in the epressions and material in said depressions atthe sides of recesses at the bottom and sides of the conthe trench.duit, said plastic concrete filling said transi ANSON MARSTON.

